Bogging down in certain conditions

So on my 82 csr750 twin, I've been having an issue with the engine bogging down the whole time ive owned it and ive been trying to figure it out with no luck. The carburetors have been totally cleaned and I put an inline filter in just to make sure. Ive adjusted the idle mixtures screws with little success though its better than it was. I have a stock air box, jets and exhaust. It happens in low rpms when I go to give it more throttle for instance, when pulling away or when im in 5th gear and go to roll on the throttle if the rpms are low. Somewhere around 3000 rpm or so and similarly when taking off from a stop. Once the engine is up to cruising rpm, I can roll and the throttle and the motor doesn't skip a beat. It idles just fine at about 1200-1500 rpm and when im moving along at higher rpms, the motor doesn't surge or sputter. It almost seems to me like a fuel delivery issue. Like the fuel cant be delivered fast enough when the rpm is low so the motor has to catch up. I wouldnt think it's a vacuum leak or my idle wouldn't be smooth. I replaced the vacuum lines going from the carb to the petcock when I rebuilt the carbs as well. Anyone have any ideas? I've really been pulling my hair out about this trying to figure it out. 

Hi, have you checked the advancer?

You say it idles fine between 1200 and1500 rpm. That is quite a bit higher than Kawasaki specifies. It should idle smoothly between 950 and 1050 rpm. If it will not, then there is a problem. Setting the idle higher may be masking the problem. Clogged pilot circuits are the most common cause. A small E string from a guitar works a treat.

The timing advancer? I'm not really sure how I could check that. Is there a process to check it with a multimeter?

Page 180.

www.kzrider.com/modules/ServiceManuals/K...l%20KZ750%20Twin.pdf

Ah okay that's for points ignition. Mine has electronic ignition. Mine has a ignition pulsing coil under the cover where points would have been on previous models of 750 twin. Im not certain of what's behind that though. I wouldnt think there would be any sort of advancer. If there is and there is a way to service it then I'll absolutely do that and if anyone has any insight on how to test the pulsing coil with a multimeter then ill absolutely also do that. If the thing is bad I'll replace it with the updated dyna s pulsing coil since you can't get an original anymore. 

No no no. My Z has also electronic ignition but once the bike was also bogging at some revs and i could not find it until i inspected the advancer. Under the advancer is a thin washer/ring witch was not ok, so i changed the wascher/ring and cleaned the little springs and a drop oil on the rotor. After that the problem was solved.  

If that is a factory system from a later model 750 twin, it will have a mechanical advancer as WillamZ900 wrote. If it is an aftermarket system, it may or may not.

Oh hell yeah! Thanks to both of you. I will check that out immediately. Any words of advice, tips tricks, things to look for or check specifically in there? Is there anything in there that I will need to adjust? I downloaded two shop manuals for the 750 twin and I didn't see anything in either for the model with the pulsing coil ignition. 

So I removed and inspected the timing advancer and it was a little dusty and there was no grease inside the body of the cam device. So I cleaned it up and put a little grease in the groove like the manual says to do then put it all back together. It didn't make any difference better or worse. That seemed like a good guess as to the possible problem but ive just got no clue what else it could be. 

Did you check to be sure the advancer is working as designed? That is, does it actually advance at the rpm specified and to the degrees specified? Some po may have replaced the orings with ones that are too strong, thus keeping the timing retarded.
Also, I believe there should be some tiny rubber bumpers for the weights to rest against. Could they be missing?

I would honestly have no clue if it is working as it is designed however I am the third owner, the previous being my father who put about 200 miles on it in 10 years and never did anything to it at all and the owner before him was his best friend who took good care of it but was not one to work on motorcycles. If anyone ever worked on the bike before me it would have been a dealership. There are no rubber bumpers but the inside of the cavity that the whole ignition system lives in is very very clean besides being a little dusty so im sure there was no rubber bumpers in it. The only other thing that I can think of is that the valves could be out of adjustment with having 20000 miles on it but I would think if the valves were out enough that it would be a problem, then the bike would run poorly across the board. Like I mentioned before the bike runs really well aside from certain situations. Besides the valves I don't know maybe the pulsing coil is going bad? I thought maybe the diaphragms in the carbs but it wouldn't run at high rpms if that was the case. I also the coil might be bad but I think that would fluctuate with temperature.